I haven't seen your other threads, so not sure how beginner we're talking. I'm not the most knowledgeable, but I'll share the best things I've discovered. :)
A lot of tutorials will tell you not to tie knots in your thread on the back hold the thread in, but instead weave it into the thread on the back. This is true if you're planning on making somethihg on a pillow or similar, but if you're framing it and don't care that the back is lumpy because no one will ever see it or feel it, just do you and make it secure.
They make cross stitch lattice thst dissolves in water, so you can cross stitch on tshirts, pillows, blankets, et cetera. It's amazing, and a game changer for making nifty little things you'll actually be able to wear or use daily. I love it so much.
Splitting your thread so its a lower ply is common, but if you leave it 6 stranded sometimes, you can add an extra layer of depth to what you make. For instance, i made a goomba (mario mushroom looking villain) for a friend. I made the outline of the goomba 6 stranded, with all the background stuff 3 stranded. It made it appear that the goomba was closer to the viewer, and really added a 3 dimensional effect that I loved. I've also used more strands to cross stitch curse words in a more handwritten font whenever i do something funny/inappropriate for the lols. Fancy script for most words in 3 strands, curse word in a scrawly looking vulgarish font with 6 strands.
Be mindful of hand pain. Carpal tunnel and damage is a real thing. Get a compression glove, take breaks. Our grandmas and mama's have carpal tunnel for a reason, don't follow in those footsteps. Take precautions.